key term - Conservation of Momentum

Definition

Conservation of momentum is a fundamental principle in physics which states that the total momentum of a closed system is constant unless an external force acts on the system. This means that the total momentum before an event, such as a collision, is equal to the total momentum after the event.

5 Must Know Facts For Your Next Test

1. Conservation of momentum is a direct consequence of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction.
2. In an isolated system, the total momentum before a collision is equal to the total momentum after the collision, even if the individual momenta of the objects change.
3. Impulse is the change in momentum of an object, and it is equal to the average force applied multiplied by the time over which it is applied.
4. In an elastic collision, kinetic energy is conserved, and the colliding objects separate after the collision with different velocities.
5. Momentum is a vector quantity, meaning it has both magnitude and direction, and it is conserved in both one-dimensional and two-dimensional collisions.

Review Questions

• Explain how the principle of conservation of momentum is related to Newton's Third Law of Motion.
  • The principle of conservation of momentum is a direct consequence of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. In a closed system, the total momentum before an event, such as a collision, is equal to the total momentum after the event. This is because the forces between the colliding objects are internal to the system, and the external forces acting on the system are negligible. The conservation of momentum is a fundamental law that ensures that the total quantity of motion in a closed system remains constant unless acted upon by an external force.
• Describe how the concept of impulse is related to the conservation of momentum.
  • Impulse is the change in momentum of an object, and it is equal to the average force applied multiplied by the time over which it is applied. In the context of conservation of momentum, impulse plays a crucial role. When two objects collide, the change in momentum of one object is equal and opposite to the change in momentum of the other object. This is because the impulse, or the change in momentum, is the result of the internal forces between the colliding objects, which are equal and opposite according to Newton's Third Law. The conservation of momentum ensures that the total impulse, or the change in momentum, of the closed system is zero, even though the individual momenta of the objects may change.
• Analyze how the concepts of elastic and inelastic collisions relate to the conservation of momentum and energy.
  • In an elastic collision, the kinetic energy of the colliding objects is conserved, and the objects separate after the collision with different velocities. In this case, the total momentum before the collision is equal to the total momentum after the collision, as per the principle of conservation of momentum. However, in an inelastic collision, the colliding objects stick together after the collision, and some of the kinetic energy is converted into other forms of energy, such as heat or deformation. Even in an inelastic collision, the total momentum before the collision is still equal to the total momentum after the collision, as the principle of conservation of momentum holds true. The distinction between elastic and inelastic collisions lies in the conservation of kinetic energy, which is a more stringent requirement than the conservation of momentum.

Related terms

Linear Momentum:

The product of an object's mass and velocity, which represents the object's quantity of motion.

Impulse:

The change in momentum of an object, equal to the average force applied multiplied by the time over which it is applied.

Elastic Collision:

A collision in which kinetic energy is conserved, and the colliding objects separate after the collision.